The word hydroscope is used to mean any of several instruments related to water.

One kind is an instrument for making observations below the surface of water,[1] such as a long tube fitted with various lenses arranged so that objects lying at the bottom can be reflected upon a screen on the deck of the ship that carries it. These are built with a large tire tube that supports the screen and covered by an acrylic dome for protection.[2]

Despite common belief, Hypatia did not invent the hydroscope, although others believe that Hypatia did help other inventors to build the instrument. Early references to the hydroscope include Synesius' description of such device in his Letter 15 and was interpreted to imply as a clepsydra or water-clock, which measures the volume of the water.[3] This historical figure was a student of Hypatia.[4]

1 'For the sake of completeness we must mention the fact that SYNESIOS in his letter to HYPATIA mentions a hydrometer, which according to some was already known in the fourth century AD to PRISCIANUS, that is a century before SYNESIOS and HYPATIA.', Forbes, 'A Short History of the Art of Distillation: from the beginnings up to the death of Cellier Blumenthal', p. 25 (1970).

4 'In 402, Hypatia receives a letter from the ailing Synesius giving a brief description of what he calls a hydroscope. This is a scientific instrument which was then in common use, although Hypatia is often credited with its invention.', Waithe, 'Ancient women philosophers, 600 B.C. – 500 A.D.', p. 192 (1987).

This technology-related article is a stub. You can help Wikipedia by expanding it.